1. Field of the Invention
This invention relates to optical deflection units. More particularly this invention relates to the use of optical polarization diversity to increase the capacity of a free-space steering unit.
2. Description of the Related Art
There are existing switching arrangements in which the polarization properties of light are relevant. U.S. Pat. No. 5,162,944 reveals a 1xc3x972 switching device where an active polarization controller is used in order to direct polarized light through different optical paths into different output ports. U.S. Pat. No. 5,381,250 describes a more complex 2xc3x972 space switch based on the same principle. This system is able to handle also unpolarized light by suitably splitting polarizations into orthogonal components and actively transforming the polarization state for each component. U.S. Pat. No. 6,134,031 discloses generalization of the principle of switching using active rotation of polarization. A plurality of units is stacked, thus increasing the size of the switch.
The invention described herein is useful in a one-dimensional scanning apparatus, enlarging capacity by a factor of about two. The technique of polarization diversity disclosed herein is also applicable to one or two-dimensional optical switches employing free-space scanning systems. The approach taken in the invention is the use of beams having two orthogonal polarizations.
In the embodiments disclosed herein, the polarization state of light is not actively altered. Polarization is combined in order to increase the capacity of optical space channels. The switching action is accomplished by steering the beam utilizing an
additional physical means, such as mirror tilting or electro-optic deflection.
In some preferred embodiments of the invention beam steering in a single plane is employed. Two N-channel deflector modules, both located in the same layer or plane of an assembly, direct polarized beams in orthogonal polarization states toward a polarization beam splitter. In some embodiments, wherein both beams are linearly polarized in the same direction, a half wave plate is interposed between one of the deflector modules and the polarization beam splitter. The polarization beam splitter combines the two beams into a single output beam, comprising 2N channels, each of which can carry a unique data stream. In alternate embodiments the group of two deflector modules and a polarization beam splitter can be stacked, optionally in combination with layers comprising a single deflector module and polarization beam splitter or mirror.
It is therefore a primary object of some aspects of the present invention to provide an improved optical arrangement for switching a large number of optical channels that is simple to manufacture, conserving of real estate, and reliable.
It is another object of some aspects of the present invention to provide an improved optical switching arrangement that can be compactly installed in an integrated device that uses optical beam deflectors, such as an optical switch or scanner.
The invention provides an optical switching arrangement, including a first deflector module, a plurality of first optical deflectors that emit a first polarized collection of beams, a second deflector module, a plurality of second optical deflectors that emit a second polarized collection of beams. The arrangement further includes a polarization beam combiner that is disposed in a first light path of the first polarized collection of beams and in a second light path of the second polarized collection of beams. The polarization beam combiner combines the first polarized collection of beams and the second polarized collection of beams into an output beam, wherein the polarization axis of the first polarized collection of beams is orthogonal to the polarization axis of the second polarized collection of beams at the polarization beam combiner. The arrangement further includes an output receiver disposed in the output beam.
According to an aspect of the optical switching arrangement, the output receiver is an array of receivers.
An additional aspect of the optical switching arrangement includes optics disposed in the output beam for focusing the output beam on the output receiver.
According to a further aspect of the optical switching arrangement, the first deflector module and the second deflector module emit light each have an identical polarization and one of them has a half-wave polarization plate disposed in the first light path.
Still another aspect of the optical switching arrangement includes optics disposed in the output beam for focusing the output beam on the output receiver.
According to yet another aspect of the optical switching arrangement, the polarization of light emitted by the first deflector module is orthogonal to the polarization of light emitted by the second deflector module.
According to one aspect of the optical switching arrangement, the first polarized collection of beams includes a plurality of first optical channels, each of the first optical channels carrying information in a beam of a corresponding one of the first optical deflectors, and the second polarized collection of beams includes a plurality of second optical channels, each of the second optical channels carrying information in a beam of a corresponding one of the second optical deflectors, wherein at least two of the first optical channels and the second optical channels carry unique streams of information.
According to an additional aspect of the optical switching arrangement, the first deflector module has N first optical deflectors, the second deflector module has N second optical deflectors, and the output receiver has 2N receivers.
According to another aspect of the optical switching arrangement, at least a portion of the first light path may be perpendicular to a portion of the second light path.
According to a further aspect of the optical switching arrangement, the first deflector module, the second deflector module, the polarization beam combiner and the output beam define a first switching subassembly, which further includes a third deflector module having a plurality of third optical deflectors that emit a third polarized beam. A mirror disposed in a third light path of the third polarized beam reflects the third polarized beam toward the output receiver, the mirror and the third deflector module, defining a second switching subassembly, wherein the first switching subassembly and the second switching subassembly are stacked.
According to one aspect of the optical switching arrangement, the first deflector module has N first optical deflectors and the second deflector module has N second optical deflectors, the third deflector module has N third optical deflectors and the output receiver has 3N receivers.
According to yet another aspect of the optical switching arrangement, the first switching subassembly includes a plurality of first switching subassemblies, wherein the first switching subassemblies and the second switching subassembly are stacked.
According to still another aspect of the optical switching arrangement, the mirror includes a second polarization beam splitter.
The invention provides a method of optical switching, including the steps of deflecting a plurality of first polarized rays to define a first polarized collection of beams, and deflecting a plurality of second polarized rays to define a second polarized collection of beams, wherein each of the first polarized rays and the second polarized rays carries a unique stream of information. The method further includes using a combiner to combine the first polarized collection of beams with the second polarized collection of beams to produce an output beam that includes the first polarized rays and the second polarized rays, wherein the polarization of the first polarized rays is orthogonal to the polarization of the second polarized rays in the output beam. The method further includes receiving the output beam in a plurality of receivers, wherein each of the receivers receives one of the first polarized rays and the second polarized rays.
An aspect of the method includes focusing the output beam on the receivers.
A further aspect of the method includes adjusting the polarization axis of the first polarized collection of beams.
According to still another aspect of the method, the first polarized collection of beams has N rays, the second polarized collection of beams has N rays, and the receivers comprise 2N receivers.
According to yet another aspect of the method, the direction of at least a portion of the first polarized collection of beams is perpendicular to a the direction of a portion of the second polarized collection of beams.
An additional aspect of the method includes deflecting a plurality of third polarized rays to define a third polarized collection of beams, providing a reflector to reflect the third polarized collection of beams toward the receivers, and stacking the reflector and the combiner.
According to one aspect of the method, the first polarized collection of beams, the second polarized collection of beams, and the third polarized collection of beams each have N rays, and there are 3N receivers.
The invention provides an optical switching arrangement, including an output receiver, a plurality of stacked switching subassemblies, the stacked switching subassemblies producing a combined output beam directed toward the output receiver. Each of the stacked switching subassemblies has a first deflector module, which includes a plurality of first optical deflectors. The first deflector module emits a first polarized collection of beams. A second deflector module has a plurality of second optical deflectors, and emits a second polarized collection of beams. Each of the stacked switching subassemblies has a polarization beam combiner disposed in a first light path of the first polarized collection of beams and in a second light path of the second polarized collection of beams, which combines the first polarized collection of beams and the second polarized collection of beams into a common beam. The common beam forms a portion of the combined output beam, wherein a polarization of the first polarized collection of beams is orthogonal to a polarization of the second polarized collection of beams at the polarization beam combiner.
According to an aspect of the optical switching arrangement, the output receiver includes an array of receivers.
Yet another aspect of the optical switching arrangement includes optics disposed in the combined output beam for focusing the combined output beam on the output receiver.
According to still another aspect of the optical switching arrangement the first deflector module and the second deflector module emit light has an identical polarization includes a half-wave polarization plate disposed in the first light path.
According to one aspect of the optical switching arrangement, a polarization of light emitted by the first deflector module is orthogonal to a polarization of light emitted by the second deflector module.
According to another aspect of the optical switching arrangement, the first polarized collection of beams includes a plurality of first optical channels, each of the first optical channels carrying information in a beam of a corresponding one of the first optical deflectors. The second polarized collection of beams includes a plurality of second optical channels, each of the second optical channels carrying information in a beam of a corresponding one of the second optical deflectors, wherein at least two of the first optical channels and the second optical channels carry unique streams of information.
According to a further aspect of the optical switching arrangement, at least a portion of the first light path is perpendicular to a portion of the second light path.